Modern electronic watches consist of an accurate electronic frequency source; CMOS divider circuitry for reducing the reference frequency to a one cycle per second signal; CMOS counters for counting minutes, seconds, hours, days, months and so on; CMOS control circuitry; and electronic displays such as a liquid crystal or light emitting diodes. This is all old. The new developments in electronic watches are occurring primarily as improvements in displays, size reduction of the circuitry, and reductions in manufacturing costs. The present invention is directed at two of these areas: namely the reduction in both size and manufacturing costs of the divider circuitry.
The divider circuitry typically consists of a series of CMOS binary divider circuits that have the property of dividing the frequency of the input signal precisely in half. That is, if the input signal frequency is 4 Hz, the output signal frequency would be 2 Hz. These circuits, although conceptually simple and old in the art, are uniquely important to digital watch design became many are required in a single watch and both space and power are limited.
Thus, it is an object of this invention to provide an improved binary circuit that is smaller in size than those currently available. Smaller size will provide higher yields and lower cost.
It is another object of the invention to provide a new binary circuit that is uniquely suited for the low power complementary metal oxide semiconductor (CMOS) process of implementation.
It is another object of the invention to provide a binary divider circuit with a minimum number of active elements.
Finally, it is an object of the invention to provide a new structure for a capacitor in CMOS.